How long does it take for a Nikon 1 battery to completely charge the first time?

I just got the Nikon 1 and I'm just wondering how long the battery needs to charge to fill for the first time.

Just let it charging until the light (green) ready comes on

Without looking at the handbook (you do have the book, don't you?) I can certainly say 'several hours'. If the charging indication does not show 'full' after 18 hours or so there's probably something wrong with the charger or the battery.
The handbook will probably give better information.